Note: Descriptions are shown in the official language in which they were submitted.
CA 02231484 1998-03-09
PATENT
ATTORNEY DOCKET NO.: RCX-13
TIThE OF THE INVENTION
SMOKING ARTICLr WRAPPER FOR CONTROLLING
IGNITION PROCLIVITY OF A SMOKING
ARTICLE WITHOUT AFFhCTING SMOKING CHARACTERISTICS
BACKGROUND OF THE INVENTION
'the present invention relates to a smoking
article wrapper composition, and a method of making
the smoking article wrapper. composition, for
significantly reducing ignition proclivity of the
smoking article without adversely affecting smoking
chara~~teristics. The invention particularly relates
to an improved wrapper paper for cigarettes wherein
treated bands on the cigarette wrapper tend to cause
the cigarette to self-extinguish if left or dropped on
a substrate before igniting the substrate.
'there is an ongoing concern in the industry to
produ~~e cigarettes having wrappers which reduce the
ignition proclivity of the smoking article, or the
tendency of the smoking article to ignite surfaces
which come into contact with the lit smoking article.
Reports have been made of fires attributed to burning
cigarettes coming into contact with combustible
materials. A justifiable interest exists in the
industry to reduce the tendency of cigarettes, or
other smoking articles, to ignite surfaces and
materials used in furniture, bedding, and the like
upon ~~ontact .
'thus, a desirable feature of smoking articles,
parti~~ularly cigarettes, is that they self-extinguish
upon lbeing dropped or left in a free burning state on
combustible materials.
It has long been recognized in the industry that
the cigarette wrapper has a significant influence on
the smolder characteristics of the cigarette. In this
CA 02231484 1998-03-09
2
regard, various attempts have been made in the art to
alter or modify the cigarette wrappers in order to
achieve the desired tendency of the cigarette to self
extinguish, or in other words to reduce the ignition
proclivity characteristics of cigarettes. Prior
references describe the application of fibrous
slurries and/or film-forming solutions to cigarette
paper to reduce permeability and control burn rate.
It has been shown that when these materials have been
appliE_d in discrete bands around the circumference of
the cigarette, the cigarette shows a reduced
propensity to ignite a substrate and has an increased
puff count.
hor example, it is known from U.S. Patent No.
4,452,,259 to define at least one circumferential band
on the wrapper of a smoking article which will
hopefully cause the smoking article to extinguish
under free burn conditions. The band is formed by
applying a liquid substance or compound to the
cigarette paper which has a liquid form in a
temperature range of about 100°C to 200°C. This
reference teaches that, as the burning cone of the
cigarette comes into contact with the band, the
compound forms a liquid film on the cigarette paper
which substantially restricts the flow of air to the
burning coal.
1:1.S. Patent No. 4,945,932 teaches another method
of providing areas of decreased air permeability which
cause the cigarette to self extinguish as the
cigarette smolders or burns into the area of reduced
permeability. The '932 patent teaches to form
patterned or annular zones in the cigarette paper by
multiple batonneing of the paper, for example, by use
of an embossing calendar.
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1;1.5. Patent No. 4,077,414 discloses the use of
printed bands of material on cigarette paper to
control the burn rate of the cigarette. Although this
reference does not particularly address ignition
proclivity, it teaches to provide relatively narrow
low porosity bands along the cigarette. The bands are
formed by applying a gel-forming substance to the
paper by painting, printing, or other coating
techniques. The reference teaches that preferred
gel-forming substances. are those which form gels in
water, such as gelatin, alginates, methyl cellulose,
methylethyl cellulose and gums. Water insoluble
substances such as lacquers and varnishes may also be
used in an organic solvent,
U.S. Patent No. 4,889,145 is another reference
that teaches of providing areas of reduced porosity
along the cigarette by applying a discontinuous
coating of a porosity reducing composition. This
reference is not particularly concerned with ignition -
proclivity of the smoking article, but with
controlling the puff count and tar delivery of the
smoking article. This. reference also teaches to
include a burn promoter in the wrapper to balance the
effect of the discontinuous coating areas.
Various other applications and processes for
reducing ignition proclivity of a cigarette are known
as, for example, by U.S. Patent No. 4,453,553; U.S.
Patent No. 4,480,650; U.S. Patent No. 4,739,775; U.S.
Patent No. 4,489,738; U.S. Patent No. 4,715,345; U.S.
Patent No. 2,666,437; U.S. Patent No. 4,622,983; and
European Patent Application 0 559 300 82.
Although, as described in the above cited
references, various meahods and processes are known
for applying discrete bands of porosity reducing
material to cigarette papers, such conventional
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techniques have a significant drawback in that a
noticeable change in the smoking characteristics of
the cigarette can be detected as the cigarette coal
burns into the treatedl bands. This is particularly
noticeable if a puff i.s be:ing drawn as the burning
coal reaches the divi~;ion between a treated and non-
treated portion of the: paper. A noticeable difference
in taste and smoke delivery is discernable by the
smoker depending on tree difference in permeabilities
between the untreated and treated sections of the
paper. Thus, what is needed, is a paper which remains
effective in reducing ignition propensity or
proclivity while minimizing the chance of discernable
changes in smoke delivery and taste to a smoker.
QBJECTS AND SUMMARY OF THE INVENTION
It is a principlE: object of the present invention
to provide a smoking article having improved ignition
proclivity characteristics.
An additional object of the present invention is
to provide a smoking article wherein the mechanism for
improving ignition proclivity does not adversely
affect smoke delivery or taste.
Still a further object of the present invention
is to provide a smoking article wrapper which
significantly reduces ignition proclivity of a smoking
article without adver=:ely affecting smoking
characteristics.
Additional objector and advantages of the
invention will be set forth in part in the following
description, or will be obvious from the description,
or may be learned through practice of the invention.
To achieve the objects and in accordance with the
purposes of the invention, as embodied and broadly
described herein, a smoking article is provided
comprising a tobacco column and a wrapper surrounding
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the tobacco column. T'he wrapper comprises discrete
areas of reduced permeability for improving ignition
proclivity characteristics of the smoking article.
The discrete areas of reduced permeability may be
5 defined as cross-direcaional bands surrounding the
smoking article. The reduced permeability areas
define a gradually changing permeability profile. For
example, the profile may gradually decrease in a
burning direction of the smoking article such that a
change in permeability in the reduced permeability
areas increases from a, zero permeability reduction to
a maximum permeability reduction in the burning
direction of the smoking article. The smoking article
according to the invention may further include an area
of sustained maximum permeability reduction following
the gradually decreasing permeability profile. The
smoking article may also include a gradually
increasing permeability profile following the
gradually decreasing permeability profile in the
burning direction of t:he smoking article with an area
of sustained maximum permeability reduction between
the gradually decreasing and gradually increasing
permeability profiles. For example, the discrete
areas may take on a romped-up and romped-down profile.
The discrete areas of reduced permeability may
comprise areas treated with a film forming solution to
reduce permeability of: the smoking article wrapper in
the treated areas. The film forming solution may
comprise any type of solution which, when dried, forms
a film which reduces permeability of the smoking
article wrapper to a level necessary for reducing
ignition proclivity, or the tendency of the smoking
article to self-extinguish if left or dropped on a
flammable substrate. For example, the solution may
comprise an aqueous solution or a non-aqueous
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solution. The non-aqueous solution may be a solution
of a aolvent soluble cellulosic polymer dissolved in a
non-aqueous solvent. The solution may also comprise a
parti~~ulate non-reactive filler material to enhance or
improve the film forming ability of the solution.
'The discrete treated areas, especially in the
embodiment wherein the: areas comprise ramp-shaped
bands, should have a width which ensures that the
smoking article will self-extinguish once the burning
coal ~of the smoking article advances into the treated
area. The width of th.e treated area is, thus, a
function of the permeability reduction of the treated
area. A desired permeability range for the maximum
sustained permeability reduction of the treated areas
is less than 6 ml/minjcm2, and generally within a
range of essentially 2 to 6 ml/min/cmz. In this
range, the area of maximum permeability preferably has
a length of at least 4 mm.
'The present invention also relates to a smoking
article wrapper, such as a cigarette paper, having
discrete areas of reduced permeability for improving
ignition proclivity control of a smoking article. The
reduced permeability areas are essentially as
described above with regards to the smoking article
according to the invention.
The accompanying drawings, which are incorporated
in and constitute a part of the specification,
illustrate embodiments. of the invention and, together
with the description, serve to explain the principles
of the invention.
ERIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a smoking
article, specifically a cigarette, according to the
invention;
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Figure 2 is a component view of the smoking
article of Fig. 1 particularly illustrating the
treated areas of the cigarette wrapper;
Figure 3 is a perspective view of a smoking
article according to the invention particularly
illustrating the ramp-:shaped treated areas;
Figure 4 is an exploded view of the cigarette
wrapper shown in Fig. a particularly illustrating the
ramp-shaped profiles of the treated areas;
Figure 5 is a cross-sectional view of the wrapper
shown in Fig. 4 taken along the lines indicated; and
Figures 6a and 6b are alternate cross-sectional
views of the ramp-shapESd treated areas formed on the
smoking article wrapped_-.
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pET.ATLED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference now will be made in detail to the
presently preferred embodiments of the invention, one
or more examples of which are illustrated in the
accompanying drawings. Each example is provided by
way of explanation of 'the invention, and not
limitation of the invention. In fact, it will be
apparent to those skilled in the art that various
modifications and variations can be made in the
present invention without departing from the scope or
spirit. of the invention. For instance, features
illustrated or described as part of one embodiment can
be used on another embodiment to yield a still further
embodiment. Thus, it is intended that the present
invention cover such modifications and variations as
come within the scope ~of the appended claims and their
equivalents.
1?igs. 1 and 2, and the following discussion
relatE~d thereto, relate to a preferred non-aqueous
solution for treating discrete areas of the smoking
artic'.Le wrapper to reduce permeability of the wrapper
in a i=rested areas to a level which tends to cause the
smoking article to self extinguish as the burning coal
of thE: smoking article advances into the treated
areas.. The discussion of Figs. 1 and 2 relates
particularly to a non-aqueous solution which
applicants have found to be particularly suited for
a
the pi~esent invention. In Figs. 1 and 2, the treated
areas are applied as spaced apart bands along the
length of the smoking article. The bands of this
embodiment do not necessarily incorporate the
decreasing and increasing permeability profiles
according to Figs. 3-6, as will be discussed more
fully below. However, the non-aqueous film-forming
solution discussed below in regards to Figs. 1 and 2
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pertains to the presenit invention in that the
respec;tive non-aqueous film-forming solution is
preferred in forming the inventive ramp-shaped bands
according to the invention.
Ia should, howeve:r, be understood that the
present invention relating to the uniquely shaped
bands or areas of reduced permeability is not limited
in any way to the non-<~queous solution discussed
herein. The present invention relates to a unique
shape or pattern for the discreted areas which can be
formed with any manner of film- forming solutions,
including non-aqueous and aqueous solutions. The
discus~sion herein related to non-aqueous solutions is
provided for means of explanation of the invention,
and a=~ an illustration of a preferred embodiment of a
particularly useful so:Lution. It should be understood
by those skilled in this art that any manner of film-
forming solutions are within the scope and spirit of
the invention. For example, the prior art describes
the application of fibrous slurries and/or any manner
of film-forming solutions to cigarette papers to
reduced permeability and control the burn rate of the
cigarEate. Aqueous so:Lutions which have been found
effective include alginate, pectin, carboxymethyl-
cellu7_ose, and polyvinyl alcohol. Fibrous slurries
applied from an aqueous solution are also effective.
These include microcryatalline cellulose, cellulon
bacterial cellulose, and highly refined wood pulp
fibers. Also, natural polymers soluble in non-aqueous
solvents are also effective. Any and all such
solutions are within the scope and spirit of the
presently claimed invention.
For purposes of e:Kplanation of the invention, the
embodiments and principles of the invention will be
discussed in regards to a cigarette. However, this is
CA 02231484 1998-03-09
for purposes of explanation of the invention only and
is not. meant to limit 'the invention only to
cigarEates. Any manner of smoking article is within
the scope and spirit of the invention.
5 The invention relates to a smoking article, and a
wrapper for a smoking article, having improved
ignition proclivity control characteristics.
"Ignit:ion proclivity" is a measure of the tendency of
the smoking article or cigarette to ignite a flammable
10 substrate if the burning cigarette is dropped or
otherwise left on a flammable substrate. A test for
ignition proclivity of a cigarette has been
estab_Lished by NIST (National Institute of Standards
and Technology) and comprises placing a smoldering
cigarette on a flammable test fabric and noting the
tendency of the cigarette to either ignite the test
fabric:, burn the test fabric beyond a normal char line
of them fabric, burn its entire length without igniting
the fabric, or self-extinguish before igniting the
test j'abric or burning its entire length.
A preferred embodiment of the invention is
illusl~rated generally in Figs. 1 and 2. A smoking
article (cigarette), generally 10, having improved
ignition proclivity characteristics includes a tobacco
column 12 within a wrapper 14. Article 10 may include
a fili~er 26. Wrapper 14 may include any manner of
commercially available cigarette wrapper, such as KC
grade 603 paper by Kimberly-Clark Corporation. It
should be understood that any other manner of paper
web may be used in this regard.
l?aper web 14 defines an outer circumferential
surface 16 when wrapped around tobacco column 12.
Discrcate areas 18 of outer circumferential surface 16
are treated with a non-aqueous solution. This
solution includes a solvent soluble cellulosic polymer
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material dissolved in a non-aqueous solvent. The
solution also includes a particulate inorganic non-
react.ive filler disbursed or suspended in the
solution, as discussed more fully below. It should
also loe understood that treated areas 18 could be
disposed on the inner surface of web 14 so as to be
adjacent the tobacco column 12.
In the embodiment illustrated, treated areas 18
are defined as circumferential cross-directional bands
24. Bands 24 are spaced apart from each other
longitudinally along the length of cigarette 10. The
bands 24, and particularly the fine particulate filler
22 are indicated in phantom in Fig. 2. However, it
should be understood that the treated areas are
essentially invisible in the formed cigarette as shown
in Fig. 1. In other words, a smoker cannot discern
from any outward sign that the wrapper 14 has been
treated in discrete areas 18. In this regard, treated
areas 18 have a smooth and flat texture essentially
the same as untreated areas 28.
Treated areas 18, or bands 24, have a
permeability within a range which is known to provide
improved ignition proclivity characteristics for the
make-up of cigarette 1Ø As the coal of cigarette 10
burns into one of bands 24, oxygen available to the
burning coal is substantially reduced due to the
decreased permeabilit~~ of wrapper 14 in the treated
areas. The reduction of oxygen causes the cigarette
to self-extinguish in the treated areas 18.
Applicants have determined that a preferred
permeability is less than 6 ml/min/cm2 (CORTESA), and
generally within a range of 2 to 6 ml/min/cm2.
Applicants have found that this range provides the
desired self-extinguisching results as the cigarette
coal burns into the treated areas.
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The width and spacing of bands 24 are dependent
on a number of variables, such as the initial
permeability of wrapper 14, density of tobacco column
12, ei~c. The bands 24 preferably have a width so that
oxygen is limited to the burning coal for a sufficient
length or period of time to extinguish the coal. In
other words, if band 24 were too narrow, the burning
coal would burn through band 24 before self-
extinguishing. Applicants have determined that, for
the cigarettes tested, a minimum band width of 4 mm is
desired.
'rhe spacing between bands 24 is also a factor of
a number of variables. The spacing should not be so
great that the cigarette burns for a sufficient length
or time to ignite a substrate before the coal ever
burns into a treated area 18. The spacing between
bands 24 also affects the thermal inertia of the
burning coal, or the ability of the coal to burn
through the treated bands 24 without self-
extinguishing. In other words, the spacing between
bands 24 should not be so great that the burning coal
burns hot enough and fast enough to burn through one
of the bands 24 when it comes into contact with the
respe~~tive band. On the other hand, the spacing
between bands 24 should not be so small that the
cigarette tends to burn out or self-extinguish in a
free :burn state. In the cigarettes tested, applicants
have found that a band. spacing of between 5 and 10 mm
is appropriate. However, it shauld be understood that
the band spacing can be any suitable width as
determined by any number of variables.
The solution applied to wrapper 14 in treated
areas 18 provides the reduced permeability in the
treated areas. Applicants have found that a non-
aqueous solution of a solvent soluble cellulosic
CA 02231484 1998-03-09
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polymer with a particulate inorganic non-reactive
filler suspended in solution works particularly well.
The non-aqueous solvent: tends not to disrupt the
inter-fiber bonding (e.g. hydrogen bonding) of the
paper web and, thus, does not significantly decrease
the strength of the paper web. Also, the non-aqueous
solvent does not cause the paper web to crinkle or
pucker when the solvent: is dried. This allows for the
wrapper 14 to have a smooth and aesthetically pleasing
l0 appearance.
Applicants have found that a particularly well
suited. non-aqueous solvent is a mixture of an alcohol
and an. acetate, for example a 50/50 mix of isopropyl
alcohol and ethyl acetate. However, it should be
understood, that this is but a preferred solvent, and
any suitable non-aqueous solvent or solvent mixture
may be: utilized in this regard. For example a 60/40
mix of normal propyl acetate and normal propyl alcohol
has also been shown to work particularly well.
Applicants have also found that a well suited solvent
soluble cellulosic polymer is ethyl cellulose in a
concentration of appro:~cimately 15% to 35% by weight of
solution and preferabl~l around 25% by weight of
solution. However, any cellulosic based polymer can
be used in this regard, including hydroxy propyl
cellulose.
1?, non-reactive inorganic particulate filler 22 is
added to the solution. Applicants have found that
filler 22 significantl~,r improves the ability of the
treatE~d areas 18 to se:Lf-extinguish the burning coal.
The solution with filler is more effective in reducing
perme~~bility of the paper web in treated areas 18.
Applicants believe than the inorganic filler 22 forms
a layE:r on the surface of wrapper 14 with the ethyl
cellulose acting as a binder or "glue" for the filler
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partic:les. Applicants believe that the filler
particles do not tend to strike into the pores of
wrapper 16 and form a relatively smooth surface
coating. The filler and cellulosic polymer form a
coherE;nt and smooth surface coating which
significantly reduces paper permeability in the
treats:d areas. It is also believed that the solution
conta:fining the inorganic filler particles is less
affeci~ed by the heat of the burning cigarette, thus
ensur:ing that the coating remains intact so as to be
effeci~ive in restricting oxygen to the burning coal.
i~ny number of inorganic fillers may be suitable
in th<~ present invention. Any filler material which
can be homogeneously disbursed in the non-aqueous
solution to form a surface film with the cellulosic
polymer without affecting the texture or appearance of
the wrapper may be used. Applicants have found that
particularly well-suited fillers are chalk, clay, and
titanium oxide.
'rhe present invention also pertains to a smoking
article wrapper for use with smoking articles, as
essentially described above, as well as a method for
makings the smoking article wrapper. The inventive
method for producing the smoking article wrapper
having improved ignition proclivity control
chara~~teristics includes applying a non-aqueous
solution of a film forming cellulosic polymer and non-
aqueous solvent with an inorganic particulate filler
material suspended in the solution to a smoking
article paper in discrete treated areas 18, such as
bands 24 as described above. The treated areas are
then dried so that essentially all of the non-aqueous
solvent is removed leaving a film of the cellulosic
material and filler material on the paper in treated
areas 18. The method includes applying the non-
CA 02231484 2005-O1-05
aqueous solution so that dried treated areas 18 have a
permeability within a range known to t:ause self-
extinguishing of the cigarettes, for example, within a
range of 2 to 6 ml/min/cm2.
5 The method also includes printincx the solution
onto the paper web in the discrete areas by means of
conventional high speed printing operations.
Applicants have found that suitable printing
techniques include gravure and flexographic printing.
10 The treated areas can be applied in the printing
operations in either a single pass or multiple passes.
The viscosity of the solution is controlled accordingly
to be suitable with the high speed printing techniques.
Applicants have also found that
15 the desired target permeability rangers are readily
achieved by applying the solution to the treated areas
in multiple passes with the conventional printing
machines. However, it is also possiblE~ to achieve the
desired permeability range by applying the solution in
a single pass and controlling the viscosity and amount
of solution applied.
The following examples relate to cigarettes
produced according to the invention and are provided
to more fully explain the invention. :Cn each of the
examples, the coatings were applied in a three pass
process without intermediate drying. The base paper
was Kimberly-Clark grade 603 paper with an average
untreated permeability of 32.6 ml/min/cm2. The
measured viscosity for the solution was 45 seconds
using a Zahn #2 Cup Viscometer.
EXAMPLE 1
In a first series, ALPHATEXTM clay (Anhydrous China
clay) by Anglo-American Clay Corporation was added to
a base solution of ethyl cellulose (approximately 25%
by weight of solution) dissolved in a 60/40 mixture of
CA 02231484 1998-03-09
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norma:L propyl acetate and normal propyl alcohol. A 10
mm band of solution was printed in a 3-pass process on
a basf~ Kimberly-Clark KC Grade 603 paper with an
initial average porosity of 32.6 ml/min/cmz. The clay
was added at 3 % weight of solution with a coat weight
of the treated areas of 3.0 g/m2. Average
permeability of this set of cigarettes was 3.1
ml/min/cm2. 3 of 3 cigarettes tested self-
extinduished at or near the coated area.
EXAMPLE 2
:In a second series, ALPHATEX clay (Anhydrous
China clay) by Anglo-American Clay Corporation was
added to a base solution of ethyl cellulose
(approximately 25% by weight of solution) dissolved in
a 60/40 mixture of normal propyl. acetate and normal
propy:L alcohol. A 10 mm band of solution was printed
in a :3-pass process on a base Kimberly-Clark KC Grade
603 paper with an initial average porosity of 32.6
ml/min/cmz. The clay Haas added at 6 % weight of .
solution. Average permeability of this set was 1.6
ml/min/cm2. 4 of 4 cigarettes tested self-
extin~~uished at or near the coated area.
EXAMPLE 3
In a third series, TiOz was added to a base
solution of ethyl cellulose (approximately 25% by
weight of solution) dissolved in a 60/40 mixture of
normal propyl acetate and normal. propyl alcohol. The
Ti02 was added in the form of a white ink. The ink
was approximately 10% Ti02 with a nitrocellulose
binder. A 10 mm band of solutian was printed in a 3-
pass :process on a base Kimberly-Clark KC Grade 603
paper with an initial average porosity of 32.6
ml/mi:n/cm2. The Ti02 was added at 0.5 % by weight of
solution with a coat weight of the treated areas being
3.4 g,/m2. Average permeability of this set was 3.2
CA 02231484 1998-03-09
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ml/min/cm2. 4 of 4 cigarettes tested self-
extinguished at or near the coated area.
EXAMPLE 4
:Cn a fourth series, Ti02 was added to a base
solut:LOn of ethyl cellulose (approximately 25% by
weighi~ of solution) dissolved in a 60/40 mixture of
norma:L propyl acetate and normal propyl alcohol. The
Ti02 was added in the :Form of a white ink. The ink
was a~?proximately 10% TiOZ with a nitrocellulose
binder. A 10 mm band of solution was printed in a 3-
pass ~~rocess on a base Kimberly-Clark KC Grade 603
paper with an initial average porosity of 32.6
ml/min/cmz . The Ti02 was added at 1. 0 % by weight of
solution with a coat weight of the treated areas being
4.2 g,/m2. Average permeability of this set was 1.8
ml/mi:n/cm2. 4 of 4 cigarettes tested self-
extin~guished at or near the coated area.
EXAMPLE 5
In a fifth series, Ti02 was added to a base
solution of ethyl cellulose (approximately 25% by
weight of solution) dissolved in a 60/40 mixture of
normal propyl acetate and normal. propyl alcohol. The
Ti02 was added in the form of a white ink. The ink
was approximately l0% Ti~z with a nitrocellulose
binder. A 10 mm band of solutian was printed in a 3-
pass ;process on a base: Kimberly-Clark KC Grade 603
paper with an initial average porosity of 32.6
ml/min/cm2. The Ti02 was added at 1.2 % by weight of
solution with a coat weight of the treated areas being
4.7 g,/m2. Average permeability of this set was 0.91
ml/min/cm2. 4 of 4 cigarettes tested self-
extinguished at or near the coated area.
EXAMPLE 6
In a sixth series;, Ti02 was added to a base
solution of ethyl cellulose (approximately 25% by
CA 02231484 1998-03-09
18
weight: of solution) dissolved in a 60/40 mixture of
normal. propyl acetate .and normal propyl alcohol. The
Ti02 was added in the i:orm of a white ink. The ink
was approximately 10% 'ri02 with a nitrocellulose
binder.. A 10 mm band ~f solution was printed in a 3-
pass process on a base Kimberly-Clark KC Grade 603
paper with an initial average porosity of 32.6
ml/min/cmz. The Ti02 was added at 2.5 % by weight of
solut~~on with a coat weight of the treated areas being
4.9 g/m2. Average permeability of this set was 0.74
ml/min/cm2. Since the permeability of this set was
less i:han the 0.91 of Example 5, it was not necessary
to te:~t for ignition proclivity. It was fully
expeci:ed any cigarettes treated with the composition
would self-extinguish.
EXAMPLE 7
=Cn a seventh series, TiOz was added to a base
solution of ethyl cellulose (approximately 25% by
weighi~ of solution) dissolved in a 60/40 mixture of
normal propyl acetate and normal propyl alcohol. The
Ti02 was added in the norm of a white ink. The ink
was approximately 10% Ti02 with a nitrocellulose
binder. A 10 mm band of solution was printed in a 3-
pass process on a base Kimberly-Clark KC Grade 603
paper with an initial average porosity of 32.6
ml/min/cm2. The Ti02 was added at 5.0 % by weight of
solution with a coat weight of the treated areas being
9.7 g/mz. Average permeability of this set was 0.29
ml/min/cm2. Since the permeability of this set was
less 'than the 0.91 of Example 5, it was not necessary
to teat for ignition proclivity. It was fully
expected that any cigarettes treated with the
composition would self-extinguish.
CA 02231484 1998-03-09
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EXAMPLE 8
In another series, MULTIFLEX chalk (precipitated
calcium carbonate) from Specialty Minerals, Inc. was
added to a base solution of ethyl cellulose
(approximately 25~ by weight of solution) in a 50/50
solvent of normal propyl acetate and normal propyl
alcohol. The chalk was added at 9 ~ weight of
solution. 5 mm cross direction bands were printed on
a base Kimberly-Clark KC Grade 603 paper with an
initial average porosity of 32.6 ml/min/cm2 in a 3-
pass c~ravure printing operation. Average permeability
for the treated areas was less than 2 ml/min/cm2. In
ignition proclivity tests conducted on a # 4 cotton
duck material with a film underneath, 3 of 5
cigarettes self-extinguished and 1 cigarette burned
its entire length without igniting the substrate. In
tests conducted on a # 6 cotton duck material without
film, 1 of 6 cigarettes self-extinguished. In this.
test, it appeared that the 5 mm band width was not
enough to extinguish the cigarette and the 10 mm band
spacing was too great to prevent an ignition.
Although, as discussed above, the printing of
cross-directional (CD) bands of permeability reducing
materials on cigarette paper has been demonstrated to
be effective in reducing permeability and ignition
propensity of cigarettes, such bands may also have an
undesirable discontinuous effect on the delivery of
smoke and taste to the smoker. These undesirable
effects may exist regardless of the type of solution
used to form the bands. For example, if the change in
permeability between the treated areas and untreated
areas of the cigarette is relatively great, the smoker
will discern a difference in taste and smoke delivery.
The applied solutions themselves may also affect the
taste of the cigarette. The present invention also
CA 02231484 1998-03-09
relates to a unique de:~ign or profile for the cross-
direct;ion bands to minimize the affect of the bands on
smoke delivery and taste to the smoker. The present
unique: design for the bands provides a more uniform
5 smoke delivery over the entire length of the
cigarette.
F~eferring particu:Larly to Figs. 3 and 4, a
smoking article 10 according to the invention is
illustrated. Again, the smoking article 10 is
10 illustrated as a cigarette but this is not meant as a
limitation of the invention. Smoking article 10
includes a tobacco column 12 surrounded by a paper
wrappE~r 14. Wrapper 14 defines an outer
circurnferential surface 16 of the smoking article.
15 Surface 16 has discrete treated areas 18 defined
thereon for reducing t:he permeability of wrapper 14,
as discussed in detail above in regards to Figs. 1 and
2. It, should also be appreciated that treated areas
18 could also be defined on the inner surface of web
20 14 so as to be adjacent the tobacco.
~Cn use, smoking article 10 is lit by a smoker at
end 13 and has a burning direction 32 towards filter
26, as commonly understood in the art. As the burning
coal of the smoking article advances in direction 32,
it evfantually meets the treated areas 18 or bands 24.
TreatE~d areas 18 are separated or spaced apart by
untreated areas 28. Thus, the burning coal alternates
in it:a progression from treated areas to untreated
areas.
According to the invention, the treated areas of
reduc~ad permeability define a gradually decreasing
permeability profile 30 in the burriing direction 32.
The gradually decreasing permeability profile 30 is
defined such that the burning coal does not engage the
maximum permeability reduction of the band 24 all at
CA 02231484 1998-03-09
21
once, but gradually burns into the area of maximum
permeability reduction. In this manner, the change in
taste and smoke delivery to the smoker occurs over a
gradual period and is less discernable to the smoker.
Referring particularly to Fig. 4, the profiles of
bands 24 are particularly illustrated. It can be
readi:Ly seen that as a burning coal of the cigarette
advances in direction 32, it first encounters area 30
of gradually decreasing permeability. In other words,
the thickness of the permeability reducing film
incre~~ses from a minimum point 34 to a maximum point
36. ~As the film increases in thickness between points
34 and 36, the permeability of the paper also
gradually decreases until it reaches a minimum
perme~~bility, or area of greatest permeability
reduction, at point 36. The coal will then burn or
advance through an area 38 of sustained maximum
reduction.
:Fig. 4 diagrammatically illustrates two types of
bands. The first band shown in dashed lines is meant
to illustrate a film formed by any type of film
forming solution, such as an aqueous solution, non-
aqueous solution, or other solution. The second band
24 sh~~wn in the burning direction 32 is meant to
illustrate a band formed with the non-aqueous solution
of a aolvent soluble cellulosic polymer dissolved in a
non-a~~ueous solvent with a particulate non-reactive
filler 22 disbursed in the solution, as described in
detail in regards to Figs. 1 and 2. However, it
should be understood, that the benefits of the unique
gradually decreasing permeability profile can be
realized regardless of the type of solution used to
form :bands 24.
'the area of sustained permeability reduction 38
preferably has a width which is great enough to cause
CA 02231484 1998-03-09
22
the cigarette to self-extinguish if it is dropped or
otherwise left on a flammable substrate. The width of
area :38 is dependent upon a number of variables,
including permeability of the treated area, type of
base paper, spacing between the bands, etc. The width
of bands 24 and space between the bands 28 can vary
accordingly. Applicants have found that, if the area
of ma:Kimum permeability reduction is within a range of
2 to ~6 ml/min/cm2, a width for area 38 should be at
least 4 mm. Also, as discussed above in detail with
regards to Figs. 1 and 2, the spacing between the
bands is also an important consideration. The spacing
should not be so great that the burning coal will
ignite a flammable substrate before it ever advances
into .a treated area. Also, the spacing should not be
so great that the burning coal generates enough
thermal inertia to burn through the treated areas
before self-extinguishing. .
,As shown particularly in Figs. 4 and 5, bands 24
may also include an area 40 of gradually increasing
permeability following areas 30 and 38 in the burning
direction 32 of the cigarette. Areas 40 of gradually
increasing permeability allow the advancing coal to
gradually burn into untreated areas 28 without
generating an abrupt change in smoke delivery or
taste.
Fig. 6a illustrates an embodiment wherein band 24
includes only a gradually decreasing area of
permeability 30 in the: burning direction 32 of the
cigarette. Similarly, Fig. 6b illustrates an
embodiment wherein band 24 includes only an area 40 of
increasing permeability.
The areas of changing permeability 30, 40 can
have a relatively smooth or flat profile, such as is
shown in the drawings, wherein bands 24 have a ramp-up
CA 02231484 1998-03-09
23
and/or ramp-down profile. Applicants have found that
this i~ype of profile can be applied directly to
wrappE:rs 14 by direct commercial printing techniques,
such as gravure or flexographic printing. The treated
areas can be applied in a multiple pass or single pass
operai~ion depending on the amount of solution applied
and viscosity of solution.
:Cn an alternative embodiment not particularly
illustrated in the figures, the areas of increasing
and decreasing permeability 30, 40 can comprise a
step-up and/or step-down profile. In other words,
bands 24 could be formed by layers having a
succe;~sively decreasing width. This type of band
could be applied in a multiple pass gravure or
flexo~~raphic printing operation.
'rhe following examples of cigarettes having CD
bands formed according to the present invention are
provided below for purposes of illustration and
explanation of the invention.
EXAMPLE 9
In this series, ramp-pattern CD bands were
printed on Kimberly-Clark Corporation KC Grade 603
paper. The ramp pattern consisted of a 2.5 mm ramp-up
area 'with coverage increasing gradually from 0 % to
100 %. A 5 mm area of maximum 100% coverage followed
the ramp-up area. A 2,5 mm ramp-down area with
coverage decreasing from 100% to 0% followed the 5 mm
area of sustained maximum coverage. The ramp pattern
was engraved on a gravure roll and used to print
cigarette papers on a commercial gravure press in a 3
pass process. The solution used was ethyl cellulose
(approximately 25% by weight of solution) in a 50/50
solvent of normal-propyl acetate and normal-propyl
alcohol with Multifle~s: chalk added at 9 % weight of
solution. With the Mu~,ltiflex chalk filler, viscosity
CA 02231484 1998-03-09
24
of the' solution was 39 cup seconds. The bands were
printed at a spacing of 10 mm. In ignition proclivity
tests conducted on a # 4 cotton duck material with a
film Underneath, 6 of 6 cigarettes self-extinguished.
In te:>ts conducted on a # 6 cotton duck material
without film, 3 of 6 cigarettes self-extinguished. In
this test, it appeared that the 10 mm band spacing was
too great to prevent an ignition in three of the
cigareattes. It will be apparent to those skilled in
the art that various modifications and variations can
be made in the present invention without departing
from i~he scope or spirit of the invention. For
examp:Le, the dimensions of the ramp-up and ramp-down
sections and area of maximum permeability reduction
can bE; varied accordingly to achieve the desired
resuli~s. Additionally, the treated areas can be
formed by any manner of solution, including aqueous
and non-aqueous solutions. Thus, it is intended that
the pi__~esent invention cover the modifications and
variai~ions of this invention provided they come within
the scope of the appended claims and their
equ iv<~ 1 ents .
3
